Munya "Manny" Horvitz was a Jewish-American gangster who was the boss of the Horvitz Gang, involved in bootlegging. Horvitz was killed in 1923 by Richard Harrow, a friend of a woman whom he had killed.

Horvitz was born in Odessa in the Province of Ukraine in the Russian Empire. Ever since the age of twelve, Horvitz dreamed of leaving for america. Horvitz was a butcher back home in Ukraine, and immigrated to the United States in 1901 because of the Russian Revolution and resumed his job as a chop house owner. With Prohibition, Horvitz bought liquor from Waxey Gordon, Mickey Doyle, and Jimmy Darmody as a front for them. However, Horvitz stopped buying from Gordon because he was charging too-high prices and made a deal with Darmody and his associates. For $50 a case, Horvitz bought 100 a week. The first $5,000 was supposed to be in advance, so Horvitz complied, but when all of the cases of liquor were bombed, Darmody was in debt to Horvitz. Horvitz kept calling him about his debt so Darmody contacted Gordon to kill him. On Sabbath, July 2, 1921, a man entered his shop claiming that there was an emergency, yelling in Yiddish. The customer was told to leave, and just then, Alfred Gordetsky entered his shop with a shotgun. Horvitz pulled a meat cleaver and struck Gordetsky in the skull, and found Heilig's Chop House toothpicks in Gordetsky's shirt pockets. When he met with Mickey Doyle, also injured, he explained that the toothpicks connected the murder case to Darmody, who owned the Atlantic City venue. Horvitz made it clear that he was going to kill Jimmy in revenge.

Horvitz headed to the Darmody Household at night, but only found Angela Darmody and her Lesbian lover. He shot both of them in rage before leaving. Soon after, Nucky Thompson killed Darmody, who had betrayed him and destroyed his empire. Horvitz worked with Mickey Doyle and Thompson in Atlantic City as their partner and was assigned with killing Rowland Smith, a beer thief, but he said that he would wait, because his wife made a great New Year's dinner.

That New Years' Eve, his wife gave him a new hat for a New Year. Just as she presented the hat, a car honked outside. He told her to wait and walked to the door, where he was confronted by Richard Harrow, who shot him under the eye with a shotgun, spraying blood on the entrance of his household. His driver was also found dead in his car outside of their house. Harrow claimed that it was revenge for Angela Darmody in a talk with Nucky, but not for Jimmy, since what Jimmy did was wrong.

Mickey claimed that he killed Horvitz so that people would fear him and pay him more money, but was kidnapped by Harrow and brought to Nucky.